Waterborne polyurethanes (WBPUs) have been studied as potential lightresponsive polymers due to their outstanding performance after incorporating light-sensitive components without decreasing their mechanical and physical properties. Photoluminescent WBPUs are lightresponsive WBPUs that can be synthesized by adding nanofillers such as carbon quantum dots and incorporating fluorophores like fluorescein, rhodamine, anthraquinone, naphthalene, and benzophenone as chain extenders or as grafting groups. These photoluminescent WBPUs can be applied as surface coatings, labels, LEDs, and fluorescent sensors. Similarly, by covalently bonding a chromophore to the WBPUs matrix, a self-colored WBPU can be synthesized, which is usually a better option than physically blending the WBPU with a coloring dye. By covalent bonding, the self-colored WBPU has lower color migration and higher water resistance and can be used in coatings, packaging, and textiles. Photochromic WBPUs have also attracted considerable attention due to their various potential applications. Photochromic WBPUs have been developed by adding small photochromic molecules (chromophores) within the polymer backbone. Different molecules such as spiropyran, spirooxazine, and azobenzene have been used to synthesize photochromic WBPUs.
